In recent years, image forming apparatus such as copy machines and printers have been endowed with various image forming capabilities, a plurality of sheet supply portions and complex paper transport paths. Thus, when a sheet jam occurs in the sheet transport path, operation efficiency is reduced in accordance with the labor of removing the jammed sheet.
For example, in the copy machine shown in FIG. 13, disposed around the image forming portion B having photosensitive drum A at its center are paper containers D and E which house paper of different sizes and supply said sheets C to the image forming portion B, and paper re-feed portion F which provides image formation to the reverse side of sheet C after image formation is completed on the obverse side when said sheet is once admitted to said image formation portion so as to make a duplex copy by forming an image on both the obverse and reverse sides of sheet C. Thereafter, sheet C, which was transported from said paper supply portion D, E and F, is fed to sheet transport path G in one vertical direction, and hence to image formation portion B through said sheet transport path G, said sheet C then being subjected to the image formation process.
Sheet transport paths H, I and J, which are disposed in the horizontal direction toward transport path G from of sheets coming from paper supply portion D, E and F, are each connected to the aforesaid vertical direction sheet transport path G at a substantially perpendicular angle, and said sheet C can readily jam at the aforesaid perpendicular junction of said paper paths.
Adoption of a construction wherein the transport paths for each transport means can be opened so as to easily remove a sheet jam, as disclosed in Japanese Examined Patent Application No. 60-223750, may be considered. However, when a jam occurs as in the situation shown in FIG. 14, the jam cannot be remedied from the other side even if the vertical sheet transport path G is opened, and although said sheet jam may be extracted from the sheet container side, such a method is difficult since the clamping feed rollers are not capable of reverse rotation and therefore provide a great deal of resistance. Thus, even if the horizontal sheet transport paths H, I and J are provided so as to be accessible by opening, the arrangement would be unsuitable relative to the vertical sheet transport path G due to the multiplicity of stages of said horizontal transport paths H, I and J. In lieu of the aforesaid configuration, extracting the sheet jam by opening the aforesaid clamping rollers may be considered.
The sheet jam removal operation becomes further complex because the operation of opening and closing the clamping transport rollers of each of the horizontal sheet transport paths H, I and J is required in addition to the operation of opening and closing the vertical sheet transport path G.